Let me kick off the Plugin a Day series with one of my favorite and indeed a must have plugin for all WordPress blogs.
Name: Spam Karma 2
Plugin Page: http://unknowngenius.com/blog/wordpress/spam-karma/
Spam Karma 2 (SK2) is an anti-spam plugin for WordPress. It is meant to stop all forms of automated Blog spam effortlessly, while remaining as unobtrusive as possible to regular commenters.
How it works:
SK2 comes feature packed with everything you need to keep your blog spam free. It includes a whole arsenal of filters that incoming comment has to go through. Each of these filters assigns a score called karma. Comments which end up with a negative karma are flagged as spam.
I’ve been using spam karma right from its early days and have been a loyal supporter of the project, the only obvious reason being its ability to keep spam off my blogs.
Installation of the plugin is extremely simple and involves you to download the file and dump the contents into your plugins folder. Activate it and visit Options > Spam Karma 2 and your ready to go.
The default settings should be good enough for most blogs out there and you always have the ability to fine tune them as I have done.
SK2 neatly lists comments in moderation and Approved Comments in two separate tabs. It has the ability to clean caught spam at regular intervals as well as cleanup the blacklists and logs, so you don’t have to do it manually.
Another good feature of SK2 is the ability to extend it using various plugins a.k.a. modules.
Are you using Spam Karma 2 on your blogs? How has the performance been so far. Any complains or suggestions?